There is a conventional technique recited in Japanese Patent Public Disclosure No. 07-314270 as an example of the clamping apparatus of this type. This prior art is mainly used to detachably fix a pallet to an upper surface of a table of a machine tool, and constructed as follows.
An annular plug portion projects upwards from the table with a tapered outer peripheral surface which narrows toward its leading end. On the other hand, the palette is provided with a tapered inner peripheral surface which engages with the tapered outer peripheral surface of the plug portion. In the clamping operation, a rod inserted into the plug portion is driven upwards. Then, the output portion of the rod pushes the pallet downwards through a plurality of engaging balls so that the tapered inner peripheral surface of the pallet makes an engagement with the tapered outer peripheral surface of the plug portion.
In the case of the prior art, once the pallet makes a strong tapering engagement with the table in the clamping operation, it becomes too difficult to release the tapering engagement in the unclamping operation, and therefore the pallet cannot be separated from the table.
The present invention aims at providing a clamping apparatus with which a movable member such as a pallet can be easily separated from a reference member such as a table, and at manufacturing such a clamping apparatus in a compact design.